“The long and short of matters then is that based on the testing we've done thus far, it doesn't look like Coffee Lake Refresh recovers any of the performance the original Coffee Lake loses from the Meltdown and Spectre fixes. Coffee Lake was always less impacted than older architectures, but whatever performance hit it took remains in the Refresh CPU design.”
For any CPU designed with the expectation of using the old method of memory access prediction without any protections... can we expect they'll ever show a significant performance recovery?
I guess I always assumed the answer was no.
The way you avoid some of the impacted scenarios (at modest performance impact) is with additional hardware or microarchitecture changes.
Basically, the task is 'Ensure processor state, as observed by another process, never changes because of speculative execution branches.'
Which is a high bar to meet, especially if you want to simultaneously optimize your execution unit utilization.